Fuel Pump issue? Advice Please!

Hey, been a while since my last post as have barely touched the car over winter… Need advice on a problem im having with the fuel pump. The fuel pump is a Bosch about 6 months old fitted to my MK1 Cabriolet with a 16v Conversion 1.8

Up until recently the fuel pump would always prime on ignition, but has now stopped. Have tested the fuel pump off the car and it seems to run okay. My first thought was the fuse possibly blown but thats fine and replaced with a new one just to be sure. And secondly i thought perhaps the relay (number 2) needed replacing have tried 3 relays and its made no difference, still no priming on ignition.

Any pointers as to what could be the problem? The pump will only make a clunk internally when i turn the key so im pretty sure its working.Thanks in advance

if the pump clunks when you turn the key the relay is at least trying to prime the pump. sounds to me like the pump is stuffed, does it run while engine is cranking? i guess car isnt starting at all right?

it may be the wirign to it is bad, check the earth is clean as well as the live.

alsoi what fuel setup have you gone for, tintop gti tank or post-84 lifter pump and reservoir?

Thanks rubjonny, thats reassuring as ive spent hours on end with wiring. am pretty confident ive got that sussed will certainly check earthing though! Correct, car doesnt start at all right now it just turns over, have tried pressing pedal but doesnt make any difference so i think the pump definitely needs to prime some fuel through the lines to metering head. i imagine ive got the tintop gti tank your referring to. could you explain the difference?

thanks

it doesnt really matter if the pump primes or not, what it does need to do though is run while the engien is cranking. if its not even doing that then either the relay, wiring or pump is knackered.

the relay needs to see a rev counter signal from the coil before it will run, so an issue with the spark system/wiring will also disable the fuel pump!

you coudl fit a 17/18 relay in the fuel pump socket, that should bring on the pump with the ignition. if not the pump or wiring is at fault. if it runs and car starts, then look at the fusebox, coil wiring or relay

appreciate your help, will have a look at these things later on and give you some feedback. Thankyou

oh and with the fuel tank, the tintop has the main pump outlet on the bottom, the later cab/rocco has a lift pump in the tank and a plastic reservoir between it and the main pump

Just a thought but maybe pump isn't priming because its full. Relay is working and starting problem elsewhere?

the relay has no way to know when its full

thanks again for suggestions guys, after spending a couple of hours last night on it, have sussed that the fuel pump although fairly new was blocked manage to unblock it no problems connect it all back up again only to hear it block up again! Took a peek inside fuel tank and it is badly rotten! New fuel tank in order. Any advice as to if i can buy a diesel 40 litre fuel tank (assuming it would be a direct fit just not sure on the hose connections) the price difference is about 70 quid and the petrol cabriolet tank is about 160. has anyone else tried this?

apologies if that was a REALLY stupid question im still quite new to all of this…

the trouble with the diesel tank is it has no swirl pot inside it, which is bad for the main pump. you need a proper gti fuel tank (make sure it has a swirl pot, cheap ones dont!)

the alternative is a post-84 cab/rocco/g40 shape polo lifter pump and fuel reservoir, then you can use a carb tank. the trouble with this is space is quite limited under the car. on the 84 cab/rocco they use a smaller accumulator which is relocated, then the reservoir goes where the accumulator used to go. have a look you'll see what i mean about the lack of room!

okay what you just said sounds like way more trouble than its worth so will bite the bullet and get the proper tank for it!

Thanks guru!